Ankylosing Spondylitis (AS) - Ankylosing spondylitis is the primary disease in the spondylitis family of diseases and is a form of chronic arthritis that primarily affects the spine, although other joints can become involved. Occurring primarily in young adults, (age of onset normally before age 35), AS causes inflammation of the spinal joints (vertebrae) that can lead to severe, chronic pain and discomfort.

Undifferentiated Spondyloarthropathy (USpA) - Undifferentiated Spondyloarthropathy (USpA) is a term used to describe symptoms and signs of spondylitis in someone who does not meet the criteria for a definitive diagnosis of AS or related disease. Over time, some people with USpA will develop a well-defined form of spondylitis such as ankylosing spondylitis.

Juvenile Spondyloarthropathy (JSpA) - Juvenile-onset spondyloarthritis (JSpA), also known as Juvenile Spondyloarthropathy, is the medical term for a group of childhood rheumatic diseases, which cause arthritis before the age of 16 and may span through adult life. JSpA typically causes pain and inflammation in the joints in the lower part of the body, for example, the pelvis, hips, knees and ankles.

Psoriatic Arthritis (PsA) - In 5-10% of those with psoriasis, arthritis also appears. In most cases, the psoriasis will precede the arthritis, sometimes by many years. When arthritis symptoms occur with psoriasis, it is called psoriatic arthritis (PsA).

Reactive Arthritis (ReA) - Reactive Arthritis (also known as Reiter's Syndrome) is a form of arthritis that can cause inflammation and pain in the joints, the skin, the eyes, the bladder, the genitals and the mucus membranes. Reactive arthritis is thought to occur as a "reaction" to an infection that started elsewhere in the body, generally in the genitourinary or gastrointestinal tract.

Enteropathic Arthritis - Enteropathic (en-ter-o-path-ic) arthritis is a form of chronic, inflammatory arthritis associated with the occurrence of an inflammatory bowel disease (IBD), the two best-known types of which are ulcerative colitis and Crohn's disease. The most common areas affected by enteropathic arthritis are inflammation of the peripheral (limb) joints, as well as the abdominal pain and possibly bloody diarrhea associated with the IBD component of the disease.

Note that the rest of this FAQ is geared toward ankylosing spondylitis (AS), the primary disease in this group of diseases. For more information on each specific disease, click on the links above.